Electric circuit interrupter



Feb. 7, 1939. w. F. SKEATS ELECTRIC CIRCUIT TNTERRUPTER Filed Feb. 18,1938 Insulation Gas Producin Material.

Inventor.

WilFred F SZ'eacs, WW6 .0

His AttOTTW e y.

Patented Feb. 7, 1939 ELECTRIC CIRCUIT INTERRUPTER Wilfred l". Skeats,Lansdowne, Pa., assignor to General Electric Company, a corporation ofNew York Application February 18,1938, Serial No. 191,233

12 Claims. (Cl. 200-144) My invention relates to electric circuitinterrupters, more particularly to air circuit breakers. and has for itsprincipal object the provision of an improved air circuit breaker of thegas-blast type having a large interrupting capacity. A circuitinterrupter of this character is disclosed and claimed in a copendingapplication, Serial No. 56,050, filed Dec. 24, 1935, by David C. Prince,for Electric circuit interrupters" and assigned to the same assignee asthe present invention.

The interruption of high voltage power arcs by a jet of liquid, such asan oil blast, produced by and in accordance with the arc pressure formedupon opening of the circuit is well known 16 and established practice inthe oil circuit breaker art. The so-called "oil-blast" circuit breakersare capable of interrupting very large power currents at high operatingvoltages with but few half cycles of arcing, and this positive actionenables D the breaker to clear a short circuit before other parts of thetransmission system are disturbed and before any damage has been done tothe circuit breaker or other apparatus.

Although recognized as a preferred method of 85 are interruption theapplication of the arc-generated blast principle to air circuit breakershas heretofore been unsuccessful, an outstanding source of failure beingin the re-ignition or reestablishing of the are after actualinterruption ll thereof by the gas blast. A further source of failurehas resided in the difficulty of avoiding heating and thus destructionof the insulating value of the gasused for blast purposes. For thesereasons practically no progress had been 88 made in applying thearc-generated blast principle to air circuit breakers notwithstandingmany years of successful and widespread use of the arc-genu-ated oilblast circuit breaker.

, I have found that an arc-generated gas blast 40 can be successfullyapplied to air circuit breakers by positioning in apredetermined mannerthe pressure-generating arc and the are or portion thereof thatls to besubjected to the gas blast, and by interposing in the blast path acooling and gas-producing material that offers comparatively smallresistance to gas flow and that actually augments the blast. In thisimproved ar-' rangement a high velocity gas blast of sumcient volume isapplied without appreciable time lag I50 to the arc to be interruptedand, upon interruption, the cooled and augmented gas blast is ofsufilcient dielectric strength to prevent re-ignition of arcing. Myinvention will be more fully set forth in the as following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing Fig. 1 is an eleva- 5 tional view, partly insection, of an air circuit breaker in the closed circuit positionembodying the present invention, and Fig. 2 is a sectional view takenalong the line 2-4 of Fig. 1.

In the specific embodiment of my invention 10 illustrated, a pair ofbreaks in series are formed within an insulating casing i by relativelymovable contact structure comprising a pair of fixed socket contacts 2and 3 of the segmental type and a movable bridging structure includingcontact rods 4 and 5 operable through the casing for engaging the socketcontacts I and I respectively. The rod contacts are electrically bridgedat I and are adapted to be moved reciprocally by an operating memberindicated at I.

The fixed contacts 2 and I are electrically connected to and mountedwithin terminal structures 2 and 3' respectively which also formextensions for receiving in the closed circuit position of the switchinsulating extensions 4' and I of the contact rods 4 and I respectively.The contact rods including the insulating tips thereof are guided forreciprocal rectilinear movement by insulating tubes 8 and l which extendan appreciable distance below the casing I and have a sleeve-like fitwith respect to the contact rods.

In the arrangement so far described lowering of the bridging member toopen the circuit results in the formation of two breaks inseries withinthe casing I. the break 2-4 being within a closed portion or are chamberI of the casing as illustrated, and the break 3-! being disposedopposite an exhaust port or chute it. This general arrangement is wellknown in the oil blast circuit breaker art above referred to, the pres-40 sure generated by the are at the break 2-4 tending to cause a blastof gas through the are at the break 3-! during exhaust from the port l0.In

-' prior attempts to utilise this gas blast for are interruption, it hasbeen found that the hot blast 46 consistingcf highly heated gases andproducts of arcing, was of such conducting nature as to be ineifectivein causing interruption so that the breaker failed. Sufilcient spacingof the;pressure-generating are from the arc to be interrupted to avoidthis diillculty resulted in an inordinately bulky and expensivestructure.

In accordance with my invention the above diillculties are eliminatedand the interrupting capacity and emciency of this type of air circuitto breaker greatly increased by closely spacing the pressure-generatingarc and the point of interruption, and by interposing a coolingstructure that is traversed by the gas from the pressuregenerating breakfor increasing the dielectric strength of said gas, said structureincluding a material which is adapted to emit additional arcextinguishing gas when subjected to the are heat and the highly heatedarc gases.

To this end the pressure-generating break 2-4 is located in acomparatively confined portion of the arc chamber l' and is closelysurrounded by a cooling structure including in the present instanceloose material II that is effective by reason of its large contactsurface not only to cool the hot gases passing across the same towardthe break 3-5 but also to yield additional gas of desirable dielectricproperties. By way of example, chopped fiber tubing in small sectionsabout A," in length has been found to be satisfactory in that itprovides a more free passage for the gas than granular material. Thisadditional gas compensates for the loss of volume due to the coolingaction of the fiber while at the same time introducing additionaldielectric between the contacts at the break 3-5.

In the specific arrangement shown the gasemitting material II isretained in an annular sieve-like structure I2 concentrically positionedwith respect to the contact rod 4. The structure I2 is provided with alarge number of openings indicated at l3 for presenting as smallresistance as possible to the flow of gas under pressure from the break2-4. Other suitable gas-producing materials can be used, if desired,further examples being boric acid, carbonates in general and urea resin.In each case the material is preferablybroken up in irregular pieces ofsuch size and shape that the interstices allow a comparatively free flowof gas through the material.

In the operation of this device opening of the circuit by lowering ofthe bridging structure is accompanied by arcs at the breaks 2-4 and 3-5respectively. As previously pointed out the are at 2-4 being within thecomparatively confined part of the arc chamber l generates considerablepressure within the chamber due to the rapid expansion of the air or gasunder influence of the arc heat. As the pressure-generating arc is drawninto the space surrounded by the fiber II, the heat of the arc, inaddition to the heat of the arc gases and are products which are drivenby the arc pressure through the annular structure l2, causesdecomposition of some of the fiber. This results in the addition ofarc-extinguishing gas of comparatively high dielectric strength to theinterrupting blast. Also, the hot arc gases in passing across the fibreand through the structure l2 are appreciably cooled so thatthe'dielectric'strength thereof is increased.

These gases combine to exhaust under pressure through the break 3-5which is preferably located at a restricted part of the exhaust l0 sothat high blast velocity at the point of interruption is assured. Thishigh velocity blast being of adequate volume and dielectric value iseffective in both positively interrupting the are within a very few halfcycles of arcing and preventing reestablishment of arcing after thecircuit has once been cleared. In certain cases it may be desirable tomake imperforate the side of the structure l2 immediately opposite thebreak at 3-5, thereby causing deflection and greater cooling of the arcgases from the break at 2-4. j

I have found that this arrangement is particularly effective in the caseof large power currents within a wide voltage range, the increasedpressure due to the large arc currents serving to interrupt arcing in avery positive manner. For the purpose of insuring equally goodperformance in the low current range where the arc pressures areobviously comparatively low, the insulating extensions or tips 4' and 5'of the contact rods are arranged "to, coact with the insulating sleeves8 and 9 respectively in the manner of an arc snufler. Normally in thecase of moderate or heavy currents; the circuit is cleared before thearcs are drawn into the tubes 8 and 9. However, in the case of lowcurrent arcs where the pressure within the arc chamber is insuflicientto produce a blast of sufiicient velocity the insulating tips 4' and 5'serve to confine the are within such a small space in the sleeves 8 and9 that a suflicient pressure is built up for are interruption.

For. the purpose of further aiding arc interruption at the break 3-5 thediverging part of the exhaust passage I0 is provided with a. pluralityof spaced insulating plates or arc splitters l4,

arranged edgewise with respect to the path of the arc. When the arc isblown by the blast into the arc splitters, it tends to draw out the areinto a fine thread at the edge of each splitter as the current zeroapproaches, and these threads are interrupted by the blast when thecurrent zero occurs.

In order to cool the exhaust gases from the breaker and so reduce oreliminate the noise and flame emission, as well as any momentaryimpairment of the dielectric strength of the surrounding air, coolingstructure may be placed in the chute defining the exhaust passage. Forthis purpose, I prefer a plurality of closely spaced very thin coppersheets l5 disposed parallel to and between the arc splitters l4. Asshown the metallic plates 15 are preferably more remotely positionedwith respect to the arc than the insulating plates l4. Also, for thepurpose of minimizing the resistance that these plates offer to flow ofexhaust gases, the effective area available for the passage of the gasesmay be increased by giving the entrance edges of the copper plates asaw-tooth or zigzag form.

Although I have shown my invention as incorporated in a double breakswitch, it will be apparent that it can readily be applied to otherforms such as, for example, a single break switch or circuit interrupterwherein one section of an arc is utilized to generate pressure for ablast that is directed through another section of the arc. In all thesearrangements the cooling and gas-producing material is interposed withrespect to the points of pressure generation and are interruption sothat the gas blast necessarily is in intimate contact with saidmaterial. It is understood that the term air as used in thespecification and claims is intended to comprehend a gas of suitabledielectric and insulating properties and is not limited to a gas atatmospheric pressure.

It should also be understood that my invention is not limited tospecific details of construction and arrangement thereof hereinillustrated, and that changes and modifications may occur to one skilledin the art without departing from the spirit of my invention.

WhatI claim as new and desire to secure by Letters Patent of the UnitedStates is:

. 1. An electric air circuit interrupter comprising an arc chamber,arcing means disposed in said chamber and located so that a section ofa,ics,sss

arc is opposite arr-exhaust opening of said chamber, another section ofare being more confined for generating arc pressure in said chamber forcausing a gas blast through said exhaust and said first section of arc,and cooling structure interposed with respect to said sections of arcpermitting substantially free fiow of said gas blast, said coolingstructure including material adapted to emit an arc-extinguishing gaswhen subjected to the are heat and thehot gases from said second sectionof arc.

2. Anelectric air circuit interrupter comprising an arc chamber,circuit-controlling means adapted to form two breaks in series in saidchamber, one of said breaks being located opposite an exhaust opening ofsaid chamber, the other of said breaks being in a more confined part ofsaid chamber so that the corresponding arc generates pressure forcausing a gas blast through said exhaust and the adjacent arc, and acooling structure interposed with respect to said breaks having a largeeifective contact surface and permitting substantially free flow or saidgas blast, said structure being composed in part of material adapted toemit an arc-extinguishing gas when subjected to the heat oi arcing atsaid pressure-generating break and to the heat of the gas blast fromsaid break passing through said structure.

3. An electric air circuit breaker comprising an arc chamber, relativelymovable contact structure separable within said chamber to cause arcing,one section of are being located substantially opposite an exhaustopening of said chamber arranged so that gas in exhausting from saidchamher is confined to a high velocity path directly traversing saidare, another section of arc being more remotely located in said chamberfor generating pressure, and cooling structure interposed with respectto said are sections so that the gases from said pressure-generating arenecessarily pass through said structure in exhausting from said chamber,said structure presenting a large cooling surface to said gas and beingcomposed in part of a material adapted to emit an arcextinguishing gaswhen subjected to the heat of the arc and the arc gases.

4. An electric air circuit breaker comprising an arc chamber, relativelymovable contacts arcooling surface to said gases.

ranged to form two breaks in series in said chamber, one of said breaksbeing opposite an exhaust passage of said chamber so that gas inexhausting from said chamber traverses at high velocity the are at saidbreak, the other of said breaks beinglocated in a comparatively confinedpart of said chamber for generating pressure causing a gas blast throughthe are at said exhaust passage, and cooling structure interposed withrespect to said breaks including a mass of material arranged to providelarge interstices and adapted'to emit an arc-extinguishing gas foraugmenting said gas blast when subjected to the are heat, said materialpermitting comparatively free fiow of the expanding gas from saidpressure-generating break while presenting'a large 5. An electric aircircuit breaker comprising ,an insulating casing forming an arc chamberhaving a restricted nozzle-like exhaust opening, relatively movablecontacts arranged to form two' breaks in series in said chamber, one ofsaid breaksbeing'directly. opposite the restricted part said exhaust,the other of said breaks beingmore remotely positioned with respect tosaid exhaust for generating arc pressure, and annular cooling structureconcentrically positioned with respect to and surrounding saidpressure-genersting. break whereby the hot gases from said breaknecessarily pass through said cooling structure in exhausting from saidchamber, said annular structure being composed in part of a large numberof fragments of material adapted to emit an arc-extinguishing gas whensubjected to the are heat at said pressure-generating break wherebetweensaid breaks arranged so that the expanding hot gases from saidpressure-generating break necessarily pass through said structure inexhausting from said chamber, said structure being composed in part of alarge number of fragments of material adapted to emit anarc-extinguishing gas when subjected to the arc heat and the heat ofsaid expanding gases whereby the effective 'gas blast through the breakat said exhaust is both cooled and augmented.

7. An electric air circuit comprising an arc chamber having an exhaustopening, relatively movable contact structure arranged to form twobreaks in series in said chahmber, said chamber being in closelyconfining relation to said breaks one of said breaks being opposite saidexhaust and the other being more remotely positioned for generating arcpressure in said chamber, cooling structure disposedin said chamber andinterposed with respect to said breaks, said cooling structure includinga mass of loose material permitting free flow of the expanding hot gasesfrom said pressure-generating break, said material also being adapted toemit an arc-extinguishing gas when in contact with said hot gaseswhereby the gas blast through,

the are at said exhaust is augmented.

8. An electric air circuit breaker comprising an arc chamber, relativelymovable contacts arranged to separate in said chamber including a fixedcontact and a movable coacting contact rod, porous structure adapted toyield an arc-extinguishing gas when subjected to are heat, saidstructure being adjacent to the path of movement of said rod contact insaid chamber whereby arc pressure generated in said chamber at largecurrents is eifective to cause an arc-extinguishing 1 gas blast throughsaid porous structure and laterally from said chamber, an insulatingsleeve arrangedto guide said contact rod along a rectilinear pathwithrespect to said fixed contact, said insulating sleeve being spaced apredetermined distance from said fixed contact, and an insulat ingmember forming an extension 01' said contact rod arranged to coact withsaid insulating sleeve for extinguishing low current arcs that are drawnthrough said chamber.

. a 9. An electric air circuit interrupter comprising an arc chamber,arcing means disposed in said chamber and located so that are is formedopposite an exhaust opening of said chamber whereby arc pressure in saidchamber is eflective to cause a gas blast through said exhaust and saidare, insulating plates forming are splitters at said exhaust for saidarc, and spaced metaliic cooling plates having high conductivitydisposed generally parallel to and between said arc splitters, saidmetallic plates being more remotely positioned from said are than saidinsulating plates. I 4 v 10. An electric air circuit breaker comprisingan insulating casing forming an arc chamber having an exhaust opening,relatively movable contact structure arranged toi'orm'two breaks inseries in said chamber, said chamber being in closely confining relationthereto, one of said breaks being opposite said exhaust and the other ofsaid breaks being more remotely positioned with respect to said'exhaustfor generating arc pressure for causing a high velocity gas blastthrough the break at said exhaust, cooling struc-. ture disposed in saidchamber and interposed with respect to said breaks, said conlingstructure including-a mass of loose material permitting free flow of gasfrom said pressure-generating break'and presenting a large coolingsurface to the expanding hotgas, said material also being adapted toemit an arc-extinguishing gas-when subjected to the are heat during thepassage of said gas therethrough whereby the gas blast through the areat said exhaust is' augmented,

and are cooling means disposed insaid exhaust opening immediately beyondthe point of arc interruption including a plurality of thin closelyPatent No. 2,1i 6,656.

auaese QERTIFlCA'I'E 0F CORRECTION.

WILFRED F. sKEATs.

spaced metallic plates having high heat conductivity and insulatingplates alternating with groups of said thin metallic plates.

11. An electric air circuit breaker comprising relatively movablecontacts. insulating structure forming an arc chute for receiving heatedarc metallic plates of high conductivity within said chute between saidinsulating plates and adjacent to the exhaust part of said chute, saidmetallic plates as a group being more re- ;motely positioned with.respect to said arc than said insulating plates.

12. An electric air circuit breaker including 7 saidare, and spacedmetallic plates having high conductivity disposed between said arcsplitters, said metallic plates being more remotely posi- -.tioned fromsaid are within said insulating plates.

" February 7,1959.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3second column, line 51, claim 7 after the word "circuit" insert breaker;line 3h, for "chahmber" read chamber; line 36, sane claim, after"breaks" first occurrence, insert a comma; page 1;, second column, line23, claim 12, for I the word "splitter" read splitters} and that thesaid Letters Patent should be read with this correction therein that thesamemay conform to the record of the case in the Patent-Office.

si ned 'and sealed this 21st day of March, A. D. i939.

(Seal) Henry Van'A'rsdale.

Acting Commissioner of Patents.

